Rendering fibrous material flame retardant with cyan amide/halomethyl phosphonic acid systems

ABSTRACT

Fibrous material such as cotton cloth is rendered flame retardant by treating the material with cyanamide and at least one halomethyl phosphonic acid represented by the structural formula:   wherein R1 represents a monovalent radical such as chloro or bromo and R2 represents a monovalent radical such as hydrogen or methyl. Durability of the flame retardancy to repeated hard water washing may be improved through a subsequent treatment with Nmethylol compounds such as methylolated melamine precondensate. A particularly high degree of flame retardancy is imparted to mercerized cotton cloth.

Uluwu pm Swidler et a1.

RENDERING FIBROUS MATERIAL FLAME RETARDANT WITH CYAN AMlDE/HALOMETHYL PHOSPHONIC ACID SYSTEMS inventors: Ronald Swidler; William A.

' Sanderson, both of Palo Alto;

William A. Mueller, Pasadena, all of Calif. Assignee: Cotton, Incorporated, New York,

Filed: July 2, 1973 Appl. No.: 375,440

Related [1.5. Application Data Continuation-impart of Ser. No. 259,350, June 2, 1972, abandoned, which is a continuation of Ser. No. 153,094, June 14, 1971, abandoned, which is a continuation of Ser. No. 862,509, Sept. 30, 1969, abandoned.

US. Cl. 428/277; 8/116 P; 106/15 FP; 427/390; 427/412; 427/392; 428/289; 428/921 Int. Cl. B06M 1/22; C09B 5/18 Field of Search 117/136, 143 A, 139.4, 117/137; 106/15 FP; 252/81; 260/5024 R, 502.4 P, 928, 941, 953, 961; 161/403;

References Cited FOREIGN PATENTS OR APPLICATIONS 6/1963 Germany I 1 SEARCH R [45] July 29, 1975 SUBSTITUTE on MISSING if? Primary Examiner-Charles E. Van Horn Assistant Examiner-J Gallagher Attorney,-Agem, or Firm-Burns, Doane, Swecker & Mathis 571 ABSTRACT Fibrous material such as cotton cloth is rendered flameretardant by treating the material with cyanamide and at least one halomethyl phosphonic acid represented by the structural formula:

iii 0 l I a -c4 H OR wherein R represents a monovalent radical such as chloro or bromo and R represents a monovalent radical such as hydrogen or methyl. Durability of the flame retardancy to repeated hard water washing may be improved through a subsequent treatment with N- methylol compounds such as methylolated melamine precondensate. A particularly high degree of flame retardancy is imparted to mercerized cotton cloth.

6 Claims, N0 Drawings CROSS REFERENCE TO RELATED APPLICATIONS This is a continuation-in-part of copending applica-i tion Ser. No. 259,350, filed June 2, 1972, now aban cloned which in turn is a continuation of application Ser. No. 153,094, filed June 14, 1971, now abandoned, which in turn is a continuation of Ser. No. 862,509, filed Sept. 30, 1969, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to flame retardant fibercontaining material and to processes forproducing the same. j

2. State of the Art I Natural fiber-containing textile materials such as cotton cloth have been employed since ancient times. However, the combustibility of these textile materials have inhibited their wider use in certain instances. A great number of flame retardants have been proposed for use with cellulosic textile materials, but these flame retardants suffer from one or more disadvantages.

A major disadvantage of many prior flame retardants is their lack of wash fastness or durability, by which is meant that while they initially render the cellulosic textile material flame retardant, such flame retardancy disappears after one or more household launderings, especially in hard water. This phenomenon is described by OBrien in Cyanamide-Based Durable Flame- Retardant Finish for Cotton." Textile Research Journal, March 1968, pp. 256-266. This article describes imparting flame retardancy to cellulosic textile materials with flame retardants of cyanamide and phosphoric acid. However, the flame retardants disclosed therein by OBrien are not resistant to hard water washing. Similarly, East German Pat. Nos. 15,357 and 18,253, and Schiffner et al in Faserforsch u. Texilteclr, l4, (9), 375-86 (1963) describe specific attempts to impart flame resistance to textile material with certain flame retardants, including combinations of urea or dicyandiamide with chloromethyl phosphonic acid, or urea with hydroxymethyl phosphonic acid, which combinations may also not be resistant or durable to repeated cycles of hard water washings, or which may unduly degrade the physical strengths of fabrics.

Other disadvantages include the relatively large quantities (high add-on) which may be necessary in order to impart flame retardance, and the undesirable alteration of other properties of the cellulosic textile material such as color, hand, and susceptibility to dye- SUMMARY OF THE INVENTION Accordingly, a primary object of the present invention is to render flber-containing material flame retardant while preventing or substantially alleviating one or more of the above-discussed disadvantages of prior processes.

tardant which does not adversely affect the other propv erties of the material."

Another object of the present invention is to provide a cellulosic flame-retarding process having improved efficiencies of reaction between the flame retardants. and the cellulosic material.

Yet another object is to provide flame resistant fibrous products produced by these processes.

Additional objects and advantages of the present invention will be apparent to those skilled in the art by reference to the following summary of the characteristic features of the present invention and the subsequent description of the preferred embodiments:

In accordance with a primary aspect of the present invention, a process is provided for rendering cellulosic and wool fiber-containing material flame retardant comprising contacting the material with cyanamide and at least one phosphonic acid represented by the structural formula:

I n ore to deposit or fix on the material a flame-retarding amount of the phosphonic acid with cyanamide. In the above formula, R represents a chloro or bromo radical and R represents a monovalent radical such as methyl or hydrogen.

A central feature of the present invention is the'discovery that cyanamide and the above described phosphonic acids can impart durable, hard water wash resistant, flame retardancy to cellulosic fibercontaining material, particularly mercerized cotton cloth. in addition, the fire retardancy-imparting systems of the present invention have improved efficiencies in terms of efficiency of reaction between the. flame retardants and the cellulose, and in terms of fire retardancy per unit add-on of phosphorus.

as indicated above is subsequently treated to improve the durability of flame retardancy to repeated hard water washing by contacting the material with at least one water-soluble compound possessing reactive N methylol groups, and thereafter curing the materialto fix or insolubilize the compound on the material.

Other aspects and advantages of the present invention will be apparent to one skilled in the art from the following:

DESCRIPTION OF THE PREFERRED EMBODIMENTS As indicated above, cyanamide (HNCNH or H NCH), also known as carbdiimide, is used along 'with certain phosphonic acids to impart the wash-resistant flame retardancy to the fibrous or fiber-containing material.

The phosphonic acids which may be suitable can be represented by the general structural formula:

where R represents a monovalent chlorine or bromine radical and R represents a monovalent radical such as hydrogen or lower alkyl. The alkyl radicals or portions of the radicals may contain, for example-from l-to 4 carbon atoms. I

Non-limiting examples of phosphonic acids having the abovedescribed structural formula and which may be used according to the process of the present invention include chloromethyl phosphonic acid, chloromethyl phosphonic acid monomethyl ester, bromomethyl phosphonic acid and bromoethyl phosphonic acid monomethyl ester. Mixtures of two or more phosphonic acids may be used if desired.

The manner in which the phosphonic acids and cyanamide are prepared or derived is per se well known and does not form a part of the present invention.

The cellulosic and wool fiber-containing materials which may be treated according to the present invention are generally any of those which have been previously employed to conjunction with known flame retardants. The fibercontaining or textile material can have a wide variety of physical forms and can be fibers, filaments, yarns, threads, and particularly woven and nonwoven cloth. The cellulosic fiber material can be cotton. flax, linen, hemp, or regenerated cellulose such as rayon (e.g., viscous rayon). Mercerized cotton may give particularly advantageous results. (Mercerized cotton is well known per se; mercerization typically comprises passing cotton through a 25 to 30 percent solution of sodium hydroxide under tension, and then washing the cotton with water while under tension. Mercerization using liquid ammonia is also known). These fiber-containing or textile materials can be mixtures of two or more different fibers, e.g., a mixture of cellulosic fibers with other fibrous materials such as nylon (e.g., nylon 6, 6), polyester (e.g., polyethylene terephthalate), acrylics (e.g., polyacrylonitrile), polyolefins (e.g., polypropylene), polyvinyl chloride, polyvinylidene chloride, and polyvinyl alcohol fibers.

The preferred cellulosic textile materials are those containing 50 weight percent or more of cotton and especially pure, i.e., essentially 100 weight percent, cotton cloth.

According to a broad aspect of the present invention, fire or flame retardancy can be imparted to fibrous material by simply contacting or impregnating the material with the phosphonic acid and cyanamide under widely varying conditions of temperature and pH.

However, durable, i.e., wash resistant, flame retard ancy is imparted only to fixing, i.e., reacting, the phosphonic acid with the cyanamide on the material. This fixing or curing" is generally accomplished by heating the treated material at superambient temperatures and at low pH. Broadly, any temperature can be employed above which the phosphonic acid and cyanamide are fixed or reacted on the material and below which undesirable thermal degradation of the material begins, and generally from 20 to 400C and preferably from l to 300C. Optimum results are obtained at l to l80C.

Durable flame retardance is imparted if. concurrently with the above described heating, the pH of the reacting mixture on the material is low, i.e., typically less than 2.5 and preferably less than 1.5, e.g., about l.0. While these pHs are believed to be critical to durability it is generally valid to assume that the pH of the reacting mixture on the material is the same as the pH of the mixture of phosphonic acid, cyanamide, and solivcnt when present, except as indicated below for the in I situ'generation of the reactants.

a used herein as the increase (dry basis) in weight of the fibrous material due to the addition of the flame retardant as a percentage of the weight of the untreated fibrous material. Examples of suitable solvents include lower alkanols such as methanol and ethanol, lower alkylene or alkyl ethers such as dioxane and ethyl ether,

1 about 0.8 or at a slightly higher pH, e.g., about 1.0 to

1.5, except as indicated below for the in situ generation of the reactants where the pH of the pad bath may vary up to about 6.0. Naturally, in the latter case the pH of the pad bath may be quite different than the pH on the material at fixation.

A method by which the above described phosphonic acids can be formed in situ is by the thermal degradation of the corresponding ammonium salt such as monoor di-ammonium chloromethyl phosphonic acid, or ammonium chloromethyl phosphonic acid monomethyl ester. For example, ammonium hydroxide can about 3.0). Thus, in the fixing step there initially-';

present, on the fibrous material, cyanamide and an ammonium salt of the phosphonic acid. Upon heating to fixation, the ammonium salt would decompose to ammonia and the corresponding phosphonic acid (resulting in a lowered pH). Usage of such ammonium salts and the inherent raising of the pH of the pad bath can be advantageous where lower pH (higher acidity) pad baths are not desired due to corrosion and personnel handling considerations.

In a preferred process for rendering fibrous materials such as cellulosic textile materials flame retardant ac cording to the present invention, the material is first contacted with an aqueous solution comprising a mixtureof phosphonic acid and cyanamide at the desired pH in a molar ratio of l:l0 to 10:1 preferably l:3 to 3:1. The excess solution is then removed from the material by any suitable means such as by passing the material between the nip of two rollers. The material is then dried to remove excess water. The drying can be accomplished at any temperature but is generally accomplished at superambient temperatures and preferably from 20 to l50C. The material is then heated in order to fix the phosphonic acid and cyanamide on the material at the above described fixation temperatures. The heating is conducted for at least several seconds and up to several hours, more typically from one to minutes. In certain instances, the fixing may be generally complete in within 2 to 10 minutes. The drying and heating steps can be conducted simultaneously but are preferably conducted sequentially. The fixing of the phosphonic acid with the cyanamide on cellulosic material is presently thought to occur in the form of a reaction product which then reacts with the hydroxyl groups of the cellulosic material.v

The treated fibrous material preferably has sufficient add-on such that it exhibits the desired degree of flame retardancy. Such materials generally have add-ons of l to 30, and preferably 10 to percent.

It is only critical to the present invention that the above described phosphonic acids and cyanamide be present on the fibrous material. Therefore, according to another embodiment of the present invention many of these compounds can be formed in situ. A preferred method by which the above described phosphonic acids can be formed in situ is by the above-described thermal degradation of the corresponding ammonium saltsuch as ammonium chloromethyl phosphonic acid monomethyl ester, or monoor di-ammonium chloromethyl phosphonic acid. Another method may be by the use of metal salts of the phosphonic acids together with means for creating the low pHs necessary to effect fixation. For example, the pH of the pad bath may be increased with sodium hydroxide, followed by the addition of ammonium chloride. Thus, in the fixing step there would be present on the cellulosic material; cyanamide, a sodium salt of the above described phosphonic acids, and ammonium chloride. Upon heating, the ammonium chloride would decompose to ammonia and hydrochloric acid converting the sodium salt to the free acid to accomplish fixation. Naturally, in these cases the pH of the pad bath may be quite'different than the pH on the material.

The solution of phosphonic acid and cyanamide into which the cellulosic material is dipped may also contain, if desired, conventional softeners, lubricants, stiffeners, brighteners, water-repellants, soil release agents, and dyes. In accordance with another aspect of the present invention, the fibrous material rendered flame retardant as indicated above is subsequently treated to improve flame retardancy by contacting the material with one or more water-soluble compounds possessing reactive N-methylol groups. When such further processing or retreatments" are employed, the acid form of the phosphonic acid residue typically needs to be regenerated such as by contacting or souring" with a dilute hydrochloride acid solution. Such regeneration is typi cally necessary due to what is throught to be inherent chemical breakdown of cyanamide to produce eventually ammonia in the curing or fixation stage, which results in an ammonium salt form of the phosphonic acid residue on the fabric. And after hard water washing, the phosphonic acid residues may inherently be present on the fabric as their calcium salts, as further explained hereinbelow.

After laundering in hard water, the phosphonic acid O Cellulose CICH,P(O) v m And generally, for a given phosphonic acid the order of flame retardant efficiency (char length) is acid monomethyl ester calcium salt.

It is thought that this subsequent treatment with N-- methylol compounds causes lowered ionicity and therefore lower susceptibility to calcium pickup (increases resistance to ion exchange) during hard water solution, and the soured fibrous material is contacted with the N-methylol compound and is thereafter curved to fix or insolubilize the compound on the material.

The water-soluble compounds possessing reactive N- methylol groups, sometimes referred to herein as N- methylol compounds, include the substantially water soluble precondensates which are obtained by condensation of formaldehyde with a compound such as melamine, or a lower alkyl-substituted melamine, or a urea. The resulting methylol-containing compound or precondensate may be further etherified by reaction with a lower alkanol such as methanol or butanol. As is well known in the fabric treating art, these precondensates are capable of being applied to fibrous materials from an aqueous solution. Good results may be obtained, for example, using precondensates obtained by condensing 1 mole of melamine or an alkyl substituted melamine with l to 6 moles of formaldehyde, i.e., using mono-, di-, tri-, tetra-, penta-, or hexa-methylol melamine. Such products function well to increase flame retardance durability and can be readily fixed or cured on fibrous material by heating as described herein. Commercially available products of this kind include Aerotex 23, an alkylate'd melamine-formaldehyde precondensate, Aerotex M-3, a dimethoxymethyl hydroxymethyl melamine: Aerotex P-225, a'hexakis (methoxymethyl) melamine; Aerotex 19, which is a less completely fractionated modification of Aerotex P-225, and Aerotex 92 which is a melamine having an average of about 1.5 methylol groups. These Aerotex products are supplied by American Cyanamide Company. Equivalent products are commercially available from other manufacturers such as Monsanto Company which produces Resloom HP, which is a melamine having an average of about 2 to 3 methylol groups/To be applied by padding, one or more of the aforementioned N-methylol compounds may be dissolved in water to form a solution containing from about 1 to 50%, preferably about 5 to 20 N-methylol compound. To facilitate insolubilization or formation of polymer on the fabric in a desired amount, it may be desirable in certain cases to add to the padding solution, a catalyst such as formic acid. citric acid, hydrochloric acid, or,

particularly, an acidacting salt such as zinc nitrate, zinc chloride, magnesium chloride, ammonium chloride, aluminum chloride, sodium hydrogen phosphate, or sodium dihydrogen phosphate. Such a catalyst may be added to the pad bath in a concentration of between lier herein in connection with the subsequent treatment with cyanamide.

Application of the N-methylol compound-containing solution to the fibrous material may be done by conventional padding using customary equipment, or by other processes well known to the art. Typically, the solutions are applied to the fibrous materials in a wet pickup of from about 40 to 120%, so as to give upon fixation a total add-on of between about 1 and 15%, based on dry fabric weight. The padding may be con ducted at ambient temperature, e.g., between about and 30C. As in the initial treatment, any excess so- 7 lution may then be removed from the fibrous material by any suitable means such as by passing the material between the nip of two rollers. The material may then be dried to remove excess water. The drying can be accomplished at any temperature but is generally accomplished at ambient or superambient temperatures, and typically from 20 to 100C. The material with the'N- methylol compound is then heated in order to fix or insolubilize the N-methylol compound on the fibrous mterial. Broadly, any temperature can be employed above which the N-methylol compound is reacted on the material and below which undesirable thermal deg radation of the material begins, and preferably from 100 to 300C, and more preferably from 120 to 180C. The heating is conducted for at least several seconds up to several hours, more typically from about 10 seconds to 2 hours and preferably from about 1 to minutes. The drying and heating steps can be conducted simultaneously but are preferably conducted sequentially.

Such treatment with N-methylol compounds has been found to reduce ionicity and calcium pickup (increasing resistance to ion exchange), thus improving durable flame retardancy. Increased durability of flame retardancy through such subsequent treatment with N- methylol compounds was unexpected insofar as the uti- 50 lization of such compound in the initial pad baths containing the phosphonic acid and cyanamide reduced flame retardancy. Moreover, other conventional creaseproofing agents such as dimethylol dihydroxy ethylene urea have been found not to increase significantly the. durability of flame retardancy. If desired, more than one subsequent treatment with additional N-methylol compound may be used.

The present invention is further illustrated by the fol- 60 lowing examples; all parts and percentages in the examples as well as in other parts of the specification and claims are by weight unless otherwise indicated. These non-limiting examples are illustrative of certain em- 65 EXAMPLE 1 'i This example illustrates the process of the present in- 'vention employing cyanamide and chloromethyl phosphonic acid (CMPA) in aqueous solutions of varying acid to cyanamide molar ratios as is shown in TABLE For each run, a weighed piece of cotton twill measuring 12 inches X 12 inches was dipped into the aqueous solution or pad bath" of cyanamide and phosphonic acid and then passed between the nip of two rollers to remove the excess solution. The cloth was then dried in an oven for 10 minutes at C and then cured (fixed) in a second oven for 15 minutes at 160C. The fabric was then washed once as described below. dried, conditioned at 65% relative humidity at 21C and reweighed. The difference between the initial weight of the sample prior to the contact with the solution and final weight of the cloth after one wash divided by the initial weight of the cloth times is recorded in TABLE I as add-on. This procedure was repeated for each of the remaining solutions.

Each of the samples was then washed the indicated number of times in an automatic home laundering machine having one wash and two rinses with intermediate spin dry operations. A hard water solution of household laundry detergent, commercially available as ALL Laundry Detergent, was employed as the wash water (pH. 8.5).- Hard water was employed in the rinses. In this example, the term hard water refers to lrvine, California, water containing a degree of hardness equivalent to 350-380 ppm of calcium carbonate. Total dissolved solids amount to 750-850 ppm. The flame retardancy was then measured according to Americal Association of Textile Chemists and Colorists (AATCC) procesure 34-1966 and the char length in pass (+)/fail vertical strip-match test was also given to each of the treated samples. In TABLE I the physical testing values are calculated by the formula:

Fill 100 Strength Retention Strength after treatment Strength before treatment TABLE 1 THE EFFECT OF PHOSPHONIC ACID:CYANAM1DE RATIO ON FLAME RETARDANCE fill Strength Retention (2) Run No. Acid Used Cyanamide AcidzCyanamide Add-On P N C1 (One Wash) in Bath (7a) Ratio ('56) (1) (11) (17) Tear Tensile I CMPA 8 1:1 12.2 1.89 0.70 1.95 71 43 2 CMPA 16 1:2 16.8 2.49 1.01 2.24 67 63 3 CMPA 24 1:3 17.8 2.53 1.49 1.60 87 56 4 CMPA 32 1:4 20.4 2.46 2.72 1.22 72 55 5 CMPA 48 I 1:6 24.0 2.25 3.30 1.08 77 60(50) Flame Retardance =Char Length (in.) and Match Test at Number of Washes Shown (ALL" Detergent) Run No. l 5 1O 2O 4O 50 80 150 1 BEL 2 1% (z) 2% 3 BEL 3 1% 1% 2 2 2 i 2% 2160-) BEL -4 1% 2 (i) 2% (:t) 3 (1) The bath also contained. in addition to the cyanamide and phosphunic acid. 0.1 percent Triton X-liX) non-ionic wetting agent and 5 percent Velvamine 380 polyethylene softener.

Value in parentheses measured in area of char. I passed match test; failed match test; (1) burned greater than 3 inches but not entire length.

In a substantially duplicate run where higher percentages of P, N and Cl were recorded. as well as a lower degree of ionicity, the flame retardance at fifty washes was 2% COMPARISON The following quantities of the following ingredients F Experiments from East German Pat. Nos. DDRP 25 were F as md'cated:

18,253 and 15,357 were carried out. The results are ingredient Grams llmmarized below, the fabric (cotton twill) pro perties chloromethyl phosphonic 66.4

being measured after a hot wash (no detergent or soap) acid monomethyl ester .unless otherwise specified. cyanam'de gzi ggfigh? l8,253--Example 1. Fusion of chloromethyl phosq Phonic acid and urea at 130C, followed y The phosphonic acid and cyanamide were mixed fabric treatment with an aqueous solution of the prodi h an amount f w t r dded to the mixture to give Cta total weight of 162 grams of solution. This solution 175%; (131%; was divided into three samples and the'pH of each ad- Char length 5% in. After an additional detergent justed to the value shown in Column 3 of TABLE 11 of a the following table with 50 wt. NaOH.

l8253EXa-ml1|e A5 1 but more dilute- For each run, a weighed piece of cotton twill measur- 155%; 032%; 071%. ing 1 2'inches X 12 inches was dipped into a solution Ch r l flgt in. After an additional detergent sample and then passed between the nip of two rollers a BEL 40 to remove the excess solution. The cloth was then dried .3 7-Ex pl Coflvefllioflal yp p y in an oven for 10 minutes at 80C and then cured in a us ng C a u second oven for 15 minutes at 160C. The fabric was 031%; N, 032%; 016%. then washed once as described below, dried, condi- Char length-BEL tioned at 65% relative humidity at 21C and reweighed. l5,357EXample 3. Soaking fabr in a luti n of The difference bet een the initial weight of the fabric CMPA and dicyandiamide at 80C for 15 min. followed sample prior to the contact with the solution and final by drying and curing. weight of the cloth after one wash divided by the initial 148%; 219%; weight of the cloth times 100 is recorded at Columns Char length-1% in. After an additional detergent 4 of TABLE II, a add-on. This procedure was re wash 6 in. peated for each of the remaining solutions. 15,357-Example 4. Fabric treated with a solution of Each of the fabric samples was then washed the indi CMPA, dried, and overtreated with a melaminecated number of times in an automatic laundering maformaldehyde product. chine having one wash and two rinses with intermediate The fabrics were so stiff that they disintegrated on spin dry operations. A dry water solution of alkyl benwashing. No measurements made. zene sulfonate, commercially available as Sears Super-concentrated Laundry Detergent, was employed as the wash water (pl-1 10.3). Hard water was employed in the rinses. The flame retardancy was then measured according to American Association of Tex- This example illustrates certain preferred embodiil Ch is and Coiorists (AATCC) procedure EXAMPLE 11 ments of the present invention employing cyanamide 34-1966 and the char length in inches is shown in CO]- with chloromethyl phosphonic acid monomethyl ester. umns 4 through 8 of TABLE 11. (The greater the char in this example, the term hard water" refers to Pasalength, the less the flame retardancy.)

dena, California, water containing a degree of hardness As may be seen from TABLE 11, at a pH of 1.0 (run equivalent to 128 ppm of calcium carbonate. Total dis- 6), flame retardance was durable for at least 20 washes solved solids amount to 236 ppm. for chloromethyl phosphonic acid monomethyl ester.

TABLE n FLAME RETARDANCE OF CMPAM:CYANAMIDE SYSTEMS Flame Retardance after Indicated Number of Washes AATCC 34-1966 (length of char) one five ten twenty thirty Add On wash washes washes washes washes Run No. Acid pH (wt (in) (in) (in) (in) Used 6 CMPAM 1.0 6.4 2% av. 4 s BEL 7 CMPAM 2.0 l 1.0 3% BEL 8 CMPAM 3.0 9.0 4% BEL Legend CMPAM chloromethyl phosphonic acid monomethyl ester BEL I burned entire length EXAMPLE Ill The solution samples were prepared by dividing up a This example illustrates certain preferred embodiments of the present invention employing cyanamide with chloromethyl phosphonic acid (CMPA) and gives a comparison to the effect of mercerization of. the cotton (flannel) fabric.

The procedure of Example I, run 2, is repeated employing the same quantities of the same ingredients and the same times, procedures and conditions with the exception that mercerized flannel cloth (Barium No. l54)is used instead of unmercerized flannel cloth (Barium No. 100) in this run (9).

The resulting flame retardany for the mercerized flannel is believed to be more durable than for the unmercerized flannel.

Mercerization'of cotton is believed to increase the number of anhydroglucose units available for reaction,

'i.e., removes" them from relatively impenetrable crystalline regions of the cellulose. Thus, when a given amount of flame retardancy-imparting reactants is applied to the cellulose, the concentration of reactive sites on a mercerized fabric is greater relative to a similar but unmercerized fabric, and hence, the efficiency of immobilization is increased (i.e., wash-off is decreased). This phenomena is significant insofar as efficiencies of reactants, durability of flame retardancy, and overall process economies are improved.

EXAMPLE IV This example illustrates certain preferred embodimerits of the present invention employing cyanamide and chloromethyl phosphonic acid (CMPA) with subsequent treatments with N-methylol compounds.

master solution into several samples, with the pH of each being adjusted to the value shown in TABLE IV with an ammonium hydroxide solution. The fabric samples were then dried in an oven for 5 minutes at C and then cured in a second oven for 5 minutes at C. The fabric samples were then washed, dried and conditioned as described in Example I except that AATCC standard phosphate detergent, equivalent to ALL detergent employed in Example I was used. and the wash and rinse water was Menlo Park, California water containing a degree of hardness equivalent to 56 ppm of calcium carbonate. Three fabric samples were used as controls, while the remaining three fabric samples were subjected to a subsequent treatment with'N- methylol compound to improve durable fire retardancy (reduce ionicity). Each subsequent treatment included dipping the fabric sample into an aqueous solution containing 10 weight percent Aerotex 92 methylolated melamine, 0.1 weight percent Triton X-IOO non-ionic wetting agent and 5 weight percent Velvamine 380 polyethylene softener. The fabric samples were then dried in an oven for 5 at 65C and then cured in a second oven for 5 minutes at 140C. Each of the fabric samples was washed the indicated number of times in an automatic home laundering machine having one wash and two rinses with intermediate spin dry operations. The flame retardancy is then measured according to American Association of Textile Chemists and Colorists (AATCC) procedure 34-1966.

As may be seen from TABLE IV, durable flame retardance is improved by such subsequent treatment with N-methyl compound.

TABLE IV SUBSEQUENT TREATMENT OF CMPA CYANAMIDE TREATED FABRICS WITH N-METHYLOL COMPOUND Subsequent Flame Retardance Run No. Treatment pH of Bath One Wash Fifty Washes P% NZ Clk ll (control) No 0.5 2 BEL 2.73 0.96 2.75 12 Yes 05 W4 2 (t) 2.40 6.50 2.13 l3 (control) No 3.0 8% BEL 2.51 l.l5 2.53 [4 Yes 3.0 W4, 4 2.01 5.6! 1.27 l5 (control) No 4.5 4% (t) BEL 2.73 0.96 1.78 l6 Yes 4.5 1% 2% (t) 2.35 5.30 L32 For each run, a piece of cotton flannel was dipped into an aqueous solution sample containing 25 weight percent chloromethyl phosphonic acid, 24 weight percent cyanamide (1:3 acidzcyanamide ratio) 0.1 weight percent Triton X-IOO non-ionic wetting agent and 5 weight percent Velvamine 380 polyethylene softener.

EXAMPLES VVl These examples illustrate certain preferred embodiments of the present invention employing cyanamide with chloromethyl phosphonic acid on wool and on rayon fabrics.

The procedure of Example I (run 2) is repeated emthe same times, procedures and conditions with the exception that the cotton twill was replaced by bleached, undyed wool in one run, by dyed wool (grey) in another run and by rayon twill in a third run. Durable flame retardance is observed for each of the treated fabrics.

operation of the present invention have been described in the foregoing specification. The invention which is since these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by of the present invention.

We claim: 1. A process for rendering cellulosic and wool fibercontaining material durably flame retardant. which process comprises the steps of:

l. contacting the material with cyanamide and at least one phosphonic acid represented by the structural formula:

intended to be protected herein, however, is not to be construed as limited to the particular forms disclosed,

those skilled in the art without departing from the spirit ploying the same quantities of the same ingredients and The principles, preferred embodiments and modes of I ill. contacting the material with an aqueous solution of at least one water-soluble compound possessing reactive N-methylol groups and curing the material to improve the durability of the flame retardancy of the material. r

2. A process according to claim 1 for rendering cotton fibercontainingtextilc material durably flame retardant, which process comprises in sequencethe steps of:

' contacting the material with an aqueous solution of cyanamide with chloromethyl phosphonic acid wherein the molar ratio of phosphonic acidzcyanamideisl:lOtol0:l,

ll. fixing the retardancy in the material at a pH less I than 1.5 by heating the material until an add-on of between about 1 and 30% is achieved and the flame retardancy becomes durable to at least 30 hard water washes; and

Ill. regenerating an acid form of fixed phosphonicacid residue on the material and then contacting the material with an aqueous solution of the N- methylol compound. and heating the material to cure and the durability of the flame retardancy is improved to at least hard water washes.

3. A process according to claim 2 wherein the textile material is mercerized cotton cloth. and wherein the aqueous mixture of cyanamide and chloromethyl phosphonic acid further contains ammonium hydroxide. and an ammonium salt of the phosphonic acid is deposited on the textile material.

4. A durably flame retardant material produced according to the process of claim 1. V g 5. A process according to claim 1 wherein the material is cellulosic and the phosphonic acid is chloromethyl phosphonic acid.

6. A process according to claim 5 wherein the cellulosic material is mercerized cotton cloth and the flame retardancy' is durable to at least 50 hard water washes.

I i t i =8 

1. A PROCESS FOR RENDERING CELLULOSIC AND WOOL FIBER-CONTAINING MATERIAL DURABLY FLAME RETARDANT, WHICH PROCESS COMPRISES THE STEPS OF:
 1. CONTACTING THE MATERIAL WITH CYANAMIDE AND AT LEAST ONE PHOSPHONIC ACID REPRESENTED BY THE STRUCTURAL FORMULA:
 2. A process according to claim 1 for rendering cotton fibercontaining textile material durably flame retardant, which process comprises in sequence the steps of: I. contacting the material with an aqueous solution of cyanamide with chloromethyl phosphonic acid wherein the molar ratio of phosphonic acid:cyanamide is 1:10 to 10:1, II. fixing the retardancy in the material at a pH less than 1.5 by heating the material until an add-on of between about 1 and 30% is achieved and the flame retardancy becomes durable to at least 30 hard water washes; and III. regenerating an acid form of fixed phosphonic acid residue on the material and then contacting the material with an aqueous solution of the N-methylol compound, and heating the material to cure and the durability of the flame retardancy is improved to at least 50 hard water washes.
 3. A process according to claim 2 wherein the textile material is mercerized cotton cloth, and wherein the aqueous mixture of cyanamide and chloromethyl phosphonic acid further contains ammonium hydroxide, and an ammonium salt of the phosphonic acid is deposited on the textile material.
 4. A durably flame retardant material produced according to the process of claim
 1. 5. A process according to claim 1 wherein the material is cellulosic and the phosphonic acid is chloromethyl phosphonic acid.
 6. A process according to claim 5 wherein the cellulosic material is mercerized cotton cloth and the flame retardancy is durable to at least 50 hard water washes. 